the sound of an internal
combustion engine; a line of depth charges was run on the bearing
indicated by the hydrophone. The motor launches and the destroyer
remained listening, until at about 6.0 P.M. a submarine came to the
surface not far from Motor Launch No. 135, which fired two rounds at the
submarine before the latter submerged. Other motor launches closed in,
and depth charges were dropped by them in close proximity to the wash of
the submarine. Oil came to the surface, and more depth charges were
dropped in large numbers on the spot for the ensuing forty-eight hours.
Eventually objects came to the surface clearly indicating the presence
of a submarine. Further charges were dropped, and an obstruction on the
bottom was located by means of a sweep. This engagement held peculiar
interest for me, since during my visit to Canada in the winter of 1919
the honour fell to me of presenting to a Canadian--Lieutenant G.L.
Cassady, R.N.V.R.--at Vancouver the Distinguished Service Cross awarded
him by His Majesty for his work in Motor Launch No. 135 on this
occasion.

_Motor Launches_ were organized into submarine hunting flotillas during
the year 1917. These vessels were equipped with the directional
hydrophone as soon as its utility was established, and were supplied
with depth charges. In the summer of 1917 four such hunting flotillas
were busy in the Channel; the work of one of these I have described
already, and they certainly contributed towards making the Channel an
uneasy place for submarine operations.

These results were, of course, greatly improved on in 1918, as the
numbers of ships fitted with the "fish" and other hydrophones increased
and further experience was gained.

The progress in supply of hydrophones is shown by the following table:

Supply of Directional
Date General Service Mark I and Shark Fin Fish
1917. Portable Type. Mark II. Type. Type.

Jul 31 2,750 500 - -
Aug 31 2,750 700 - -
Sep 30 2,750 850 - -
Oct 31 3,500 1,000 - -
Dec 31 3,680 1,950 870 37

HYDROPHONE STATIONS AND TRAINING SCHOOLS

At the beginning of 1917 four _shore hydrophone stations_ were in use.
During the year eight additional stations were completed and several
more were near